This disclosure generally relates to a method and apparatus for wireless communications, and more particularly relates to a technique for full-duplex transmission in many-antenna multi-user (MU) multiple-input multiple-output (MIMO) systems.
Full-duplex wireless communication, in which transmission and reception occur at the same time and in the same frequency band, has the potential to as much as double the spectral efficiency of traditional half-duplex systems. The main challenge to full-duplex communication is self-interference, i.e., a node's transmit signal generates high-powered interference to its own receiver. It has been shown that full-duplex operation may be feasible for small cells (e.g., small number of users), and the key enabler has been analog cancellation of the self-interference in addition to digital cancellation. Analog cancellation has been considered a necessary component of a full-duplex system, to avoid self-interference from overwhelming a dynamic range of receiver electronics, and swamping the much weaker intended signal.
Many analog cancellation designs have been proposed for single-antenna and dual-antenna full-duplex systems. However, current wireless base stations utilize many antennas (e.g., up to eight antennas, such as in Long Term Evolution (LTE) Release 12 based systems), and next-generation wireless communication systems will likely employ many more antennas at base stations. For example, discussions to include 64-antenna base stations have already been initiated in 3rd Generation Partnership Project (3GPP) standardization, and “massive” antenna arrays with hundreds to thousands of antennas have also been proposed for 5th generation (5G) wireless communication systems.
As the number of base-station antennas increases, an important question is how to enable full-duplex with a large number of antennas. Full-duplex multi-user multiple-input multiple-output (MU-MIMO) communications would enable the base station to transmit to multiple downlink users and receive from multiple uplink users, all at the same time and in the same frequency band. Full-duplex with many antennas presents both challenges and opportunities. The complexity of analog self-interference cancellation circuitry grows in proportion to the number of antennas. At the same time, many-antenna full-duplex also presents an opportunity: having many more antennas than users served means that more spatial resources become available for transmit beamforming to reduce self-interference.